1. Technical Field
This disclosure relates to a waste liquid container and an image forming apparatus.
2. Description of the Related Art
As for known image forming apparatuses, there are printers, facsimile machines, copiers, and multi-function machines. One example of such image forming apparatuses is a liquid jet recording apparatus (e.g., inkjet recording apparatus). The liquid jet recording apparatus performs an image forming (also referred to as “recording”, “printing” and the like) operation by using a recording head that ejects droplets of recording liquid (ink droplets) to a medium (e.g., paper, OHP sheet, also referred to as “recording medium”) onto which the ejected liquid droplets can adhere. The liquid jet recording apparatus includes, for example, a serial type image forming apparatus that forms images by ejecting liquid droplets while moving the recording head in a main scanning direction or a line type image forming apparatus that forms images by ejecting liquid droplets without moving the recording head.
It is to be noted that the medium on which liquid is ejected from the image forming apparatus includes materials such as paper, string, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic. Furthermore, the term “image formation” not only includes forming images that have a meaning (e.g., letters, shapes) on a medium but also includes forming images having no particular meaning (e.g., patterns). Furthermore, the term “liquid” not only includes recording liquid and ink, but also includes any liquid which can be used to form images. Furthermore, the term “liquid jetting apparatus” includes an apparatus that ejects liquid from a liquid jet head.
The image forming apparatus including the liquid jetting apparatus may be provided with a maintenance/recovery mechanism for maintaining/recovering the performance of a recording head from which liquid (e.g., ink) is ejected. The maintenance/recovery mechanism seals a nozzle plane (plane of the recording head in which nozzles are formed) of the recording head with a cap member and connects the cap member to an absorbing pump having a pumping tube, and drives the absorbing pumping, to thereby forcibly discharge ink from the nozzles of the recording head. Furthermore, the maintenance/recovery mechanism performs blank ejection for ejecting ink droplets that do not contribute to image formation.
By operating the maintenance/recovery mechanism, waste liquid not contributing to image formation is discharged to a waste liquid container provided in the image forming apparatus for storing the waste liquid (also referred to as “waste liquid containing unit”, “waste liquid tank”, and “waste ink tank”). The image forming apparatus stops operations when the waste liquid container is full or nearly full.
As a waste liquid container according to a related art example, Japanese Registered Patent No. 85143 (hereinafter referred to as “Patent Document 1”) discloses a waste liquid container including a reservoir area for storing waste ink, an ink receiving area for receiving waste ink discharged from a pumping apparatus and guiding the waste ink to the reservoir area, a non-reservoir area situated next to the ink receiving area for removing the waste liquid, a first ink absorbing member provided in the ink receiving area for absorbing waste ink, and a second ink absorbing member provided in the reservoir area for absorbing waste ink.
Japanese Laid-Open Patent Application No. 2006-137079 (hereinafter referred to as “Patent Document 2”) discloses a waste liquid container for containing waste liquid by separately containing accumulated matter and liquid matter included in the waste liquid. This container is provided with a notch part and a space into which the waste liquid is introduced. The accumulated matter is contained in the space, and the liquid matter is absorbed by an absorbing member.
Furthermore, Japanese Laid-Open Patent Application No. 2000-85143 (hereinafter referred to as “Patent Document 3”) discloses a waste ink tank able to detect whether the waste ink tank is full. This waste ink tank has a waste ink inlet at one end of an upper wall of the waste ink tank and a detection window at the other end. A white sponge and an optical detection sensor are provided at a lower part of the detection window for detecting whether the optical reflectance of the sponge is equal to or less than a predetermined value as the color of the sponge changes to black as the waste ink is absorbed by the white sponge. The waste ink tank detects that the tank is full when hardly any light is incident on the optical sensor.
Furthermore, Japanese Laid-Open Patent Application No. 2000-141704 (hereinafter referred to as “Patent Document 4”) discloses a waste ink collecting mechanism having a part for counting the number of times performing a maintenance operation. Accordingly, it is determined whether a tank is full by estimating the amount of waste ink based on the counted results and comparing the estimated amount with a predetermined amount.
Furthermore, Japanese Laid-Open Patent Application No. 2004-136550 (hereinafter referred to as “Patent Document 5”) discloses an inkjet recording apparatus that determines whether a waste ink tank is full by estimating the total amount of waste ink discharged to the waste ink tank and comparing the estimated total amount with a reference value that is increased along with the passing of time.
Furthermore, Japanese Laid-Open Patent Application No. 2006-159465 (hereinafter referred to as “Patent Document 6”) discloses an image forming apparatus including a waste liquid container configured to store accumulated ink in the vicinity of a waste liquid inlet and absorb liquid waste ink by providing an absorbing member at areas other than the vicinity of the waste liquid inlet. The image forming apparatus detects whether its tank is full by detecting the accumulated ink by calculating the number of times performing a maintenance operation and comparing the calculation results with a reference value.
Since the waste liquid containers disclosed in Patent Documents 2 and 6 are configured having a thin waste liquid containing space and a thick waste liquid containing space divided by a partitioning plate or an absorbing member, replacement of the container may be required when one of the spaces become full even if there is still room available for containing waste liquid in the other one of the spaces.
As described in Patent Documents 2 and 6, pigment type ink has higher viscosity and loses fluidity (due to evaporation of its solvent) faster compared to a typical dye type ink. Therefore, in a case where the pigment type ink is discharged into the waste liquid container, the pigment type ink loses fluidity and accumulates in the vicinity of the inlet of the waste liquid container. In a case where there is such an accumulation of waste liquid, the waste ink tank disclosed in Patent Document 3 configured to determine whether its tank is full on the premise that the waste ink has fluidity may be unable to determine that its tank is full due to the accumulated waste liquid overflowing from its waste liquid inlet.
Furthermore, with the waste liquid containers disclosed in Patent Documents 4 through 6, each of which determines whether its tank is full by estimating the amount of waste liquid by comparing it with a predetermined threshold, the precision of the determination largely differs depending on the precision of the calculating part (threshold value) since determination is made without measuring the actual amount of waste ink. Therefore, in a case where the criterion for the determination is assumed with a high safety margin, the tank may be determined as being full at an early stage even if there is still sufficient room available for containing the waste liquid. As a result, the waste container cannot be sufficiently used (short service life). On the other hand, overflow of the waste liquid may occur in a case where the criterion for the determination is assumed with a low safety margin or a case where the waste liquid tank is used under conditions (environment) different from the conditions assumed for obtaining the threshold value.